I've been lootranking things for a while now, so I LOVE this addon. (Goodbye printed list for raid-checking gear).

Anyway, I see there are requests for scales, so I thought I'd submit mine, and the rational behind it.

Int = 1
Spirit = 1.25
Spellpower = 1
MP5 = 3
Crit = .55
Haste = .47

The big balancing point here is Mana regen and Spellpower. The way I play, (try to abuse the 5sr) Int & Spirit ranks pretty highly for regen. But with WotLK raids, time outside the 5sr is fleeting at best, so I've found that 1 mp5 is worth roughly 3 spirit for regen purposes. So for each Mp5 I get the same result for 3 spirit.

With current mana regen calculations, 1 spirit is roughly equivalent to 1 Int.

Spirit also however affects Spellpower (1/4 of spirit is converted via talents), so I've put a bit of extra weight on spirit.

I then fiddled heavily with the other numbers until I got a lootrank (www.lootrank.com) list that listed items in a priority that I thought was appropriate. Crit being a bit more important than Haste in my book, but not weighted heavily enough to skew the more important stats.

So, that's my list, and why the numbers are the way they are. Hope it helps! ;)